Hydraulic press surge control



Dern 26, 1933. W, ERNST 1,940,668

HYDRAULIC' PRESS sURGE CONTROL;

Fil'd March l23, 1931 I. Il il l i l l E l l I A elA l l :nl nventor, .,4;

Gttornegs.

2 sheets-sheet 1 26, 1933. w. ERNST HYDRAULIC PRESS SURGE CONTRL 2 Sheets-Sheet 2 Filed 4Marh 23 1931 www WYMMJWW 4 1 W 3 3 J7 /0 Gttornegs.

Patented Dec.' 26, 1933 1,940,668 HYDRAULIC rnn'ss sUnGE ooN'raoL Walter Ernst, Mount Gilead, ohio, assigner to The Hydraulic Press Manufacturing Company,

Mount Gilead, Ohio Application March 23, i931. Serial No. 524,692

d Claims. (Cl. i3d-llt) This invention relates to hydraulic presses or other similar machinery 'in which a platen is moved in one or opposite directions by hydraulic pressure applied atdiferent stages of the travel 5 of the platen to rams of different areas to cause the platen to travel faster or slower during cern tain phases of operation. y

Such an apparatus is exempliiied inthe hy draulicpress shown herein and wherein is em-` bodied a platen, a main cylinder and large area ram to force the 'platen in one direction and a push-back cylinder and small area ram to' force the platen in the opposite being connected in` a com direction, the cylinders mon hydraulic circuit including a pump which is reversible to cause one or the other of the ment of the platen. The

rams to control movedifferential in ram displacements during the phases of operation oi apparatus of this vide a surge in the pump type makes it necessary to protanlr and a surge valve connected circuit so that the pump may at timesdraw4 upon the tank supply, and so that pressure fluid may surge back and forth between the tanlrand the main cylinder to compensate for 'the displacement reversal of the pump.

it is desirable to employ differential occasioned by area so as to reduce to the minimum resistance to flow between the main cylinder and the surge tanlr. Naturally, the larger the area of the surge valve, the greater will be ing movement of the valve within the main cylinder.

open suddenly in order within the the resistance to openset up by pressure To force this. valve to free fluid pressure main cylinder and thus enable the push-back ram to beoperated, would result in a considerable shock to the apparatus which is very undesirable.

Therefore, it is an object of my present invention to provide a novel means for first bringing about a reduction of pressure in the main cylinder and thereafter permitting pressure cylinder into the surge In its detailed na ure fluid opening the surge valve and to flow from the main tank. l v

the invention resides in the provision in a hydraulic press embodying a platen, a main cylinder and large area ram to project the platen, .small area ram to an auxiliary cylinder and retract the platen, a surge tank, a surge valve controlling communication between the main cylinder and the tank and capable of being opened automatically when the platen is projected, a pressure actuated plunger for forcing the surge valve open during the retractive movement of the platen, and a reversible a surge valve of large pump having its pair of composite intake and output ports connected in circuit with the main and auxiliary cylinders; of a surge control unit having a pressure chamber connected by one pipe with the pump port connected with the auxiliary cylinder, and by another pipe in communication` with the pressure `actuated plunger, said pressure chamber being in communication through a check valve with the interior of the 'surge tank, and a check valve unseating plunger communi- 35 eating through a branch pipe line with the pressure circuit line between the main cylinder and the remaining composite pump port so that theV plunger will be pressure actuated to hold the -check valve unseated whenever pressure `is built TND up in the main cylinder and release and permit seating of the check valve when pressure in the main cylinder is suitablyreduced to cause pump pressure to be exerted on the pressure actuated plunger for the purpose of unseating the surge 'Kb' valve.

mother object of the invention is to provide a surge control unit so constructed as to adapt it for being mounted directly in the surge tanlr.

Other objectsD will in part be obvious and in part` be pointed out hereinater.

The invention. still further resides in the novel details of construction, the combination and arrangement o parts, all of which will be rst fully described in the following detailed* description, then be particularly pointed out'in the appended claims, reference being had to the accompanying drawings, in which:-

' Figure l is a somewhat diagrammatic side elevation illustrating the invention in use upon a hydraulic press,` parts being broken away and in section;

Figure 2 is an enlarged view illustrating the main cylinder, the surge tank, the surge valve and the surge control unit in detail section, the remainder of the operating circuit being indicated diagranmiatically; the position of the parts at the beginningl of the platen ,push-back function being illustrated in full lines, and the change of position of the valves gradually effected by reduction of pressure in themain cylinder being illustrated in dotted-lines.

The invention\ may be embodied in various types of pressesemployed for Various purposes, but is illustrated in connection with a press of the four column downward pressure type includ` ing push-back ram and cylinder equipments for returning the platen and control devices for causing the platen to operate through a cycle, name- 110 lil ly, an advance or working stroke and a retractive or return stroke.

There is shown a base A and a head B which is supported upon the base by four strain rods C in the usual manner. The platen is designated D and the main cylinder E is supported upon the head, while the push-back cylinders F may be supported by the strain rods. Asurge tank G is mounted directly upon the main cylinder E. A reversible pump H serves to suitably force the pressure fluid through the pressure circuit under control of the control devices indicated at I in order to operate the platen through successive cycles when the press is in actual use.

All of the equipment above-described is more or less conventional and the specific details thereof form no part of my present invention. The pump is preferably of the Hele-Shaw type such as is disclosed in U. S. Letters Patent No. 1,250,170, issued December 18, 1917, and the control device, generally designated I, is disclosed in detail in U. S. Letters Patent No. 1,711,378 issued April 30, 1929.

In the drawings, designates the main ram which is of large area and operates in the main cylinder E, passing through a suitable gland 6 for connection with the platen D. Small area push-back rams 7 are operable in the push-back cylinders F and project through glands 8 for connection with the platen. The general operation of presses of this type is well understood. The platen initially proceeds downwardly under action of lgravity until it comes in contact with..

the work when pressure will be built up and the pressing function of the platen accomplished thereby in the usual marmer. As described in Patent 1,711,378, above referred to, the pump is automatically reversed when a certain pressure is built up in the main cylinder and the pump then acts to bring the push-back rams into operation for forcing the platen upwardly. The relative areas of the main and push-back rams provide for a relatively slow working stroke and a relatively fast return stroke of the platen in the usual manner. f

The surge tank G is. flange connected as at 9 directly upon the main cylinder Eand the surge tank communicates with the interior of the main cylinder through the relatively large opening'controlled by the surge valve generally designated J It is desirable that this surge valve should have the largest possible area so that when communication is opened between the surge tank and the main cylinder the freest possible ow of iiuid is provided for to overcome any tendency toward a throttling effect.

The surge valve disclosed herein comprises a cylindrical valve-casing 10 positioned in an opening 11 in the top of the cylinder Eand' extending downwardly into the cylinder, the casing-.ageing provided with a peripheral flange 12 positioned in a seat 13 on the top of the cylinder. The valve casing is clamped in place by means of a clamping ring 14 which forms part of a separate casing .member 15 disposed directly abovethe casing 10 and which is drawn downwardly against the flange 12 by means of suitable securing bolts 16.

The valve casing 10 .is formed with a bore 17, the upper end portion of which is of reduced diameter. This bore faces directly toward the surge tank and communicates therewith by means of a plurality of openings 18 in the separate casing member 15. .'Ihe bore communicates with the main cylinder by means of a plurality `of radial passages 19 extending through the casing 'main lram will tend to create a suction in this and lying in a common horizontal plane disposed substantially at the vertical center of -the casing 10.

A valve element 20 is mounted for vertical sliding movements within the bore and is provided with a plurality of vertically extending ribs or wings 21 which cooperate with the reduced upper' portion of the bore for guiding the valve element. This element is formed with a seat engaging surface 22 which is tapered outwardly 85 and downwardly and which is adapted to seat upon a peripheral seat 23 formed in the bore 17, the seat being similarly tapered outwardly and downwardly and being above and immediately adjacent to the radial passages 19.

The lower part of the valve element 20 is hollow and accommodates a spring 24 interposed between a plate 25 secured to the lower end of the casing 10 and a spring seat 26 formed in the hollow part of the valve element. The plate 25 9; is perforate as at 27 and is provided with a spring centering rib 28. The spring 24 is just strong enough to maintain the valve element in its upper position against its own weight and is readily yieldable to form the element to move outwardly 19k when the pressure on the lower side thereof is slightly less than that on the upper side.

In operation when the platen moves downwardly, the vacating of the main cylinder by the cylinder. As soon as this takes place the static pressure due to the head of fluid in the surge tank will move the valve element 20 downwardly and fiuid will iiow downwardly from the surge tank 3 through the openings 18, the spaces between the ribs 21 and thence through the radial passages 19 into the cylinder E.

It will be observed that with the exception of the change from downward to outward ow at the plane of. radial passages 19, the iiuid has a .direct and unobstructed vpath through which to travel in passing from the surge tank to -the main cylinder so that a minimum of resistance to fluid flow is offered. The drag or the descent ofthe platen and the throttling eiect due to the usual restriction of surge flow is therefore reduced to a. minimum andmore efficient operation ofthe press is made possible.` It will also be observed vthat due to the particular arrangement of the valve engaging surface 23, the fluid is deflected 125i smoothly forward through passages 19 so that no'seriously abrupt changes in the direction of fluid flow take place. y

In certain kinds of press operating circuits, such as lthat illustrated in the accompanying drawings, it is necessary that the surge valve be opened when uid is introduced into the pushback cylinders F to elect the return movement of the platen. This is necessary in order to provide for the expellingl from the cylinder E of the fluid remaining therein at the end of a working stroke. In order to accomplish this I provide a pressure actuated plunger 29 mounted for vertical sliding movements in a bushing 30 in the separate casing member 15, the upper end of the plunger extending into a pressure chamber 31 closed at its upper end by means of a plate 32. A spring 33 is interposed between a head 34 on the upper end of the plunger 29V and the .top face of the bushing, this spring serving to normally maintain the plunger out of contact with the movable valve element 20.

As before stated the retractive or upward travel of the platen D, occasioned by the push-back cylinders F and rams 7, is much faster than the 150 the main cylinder E, provision must be made for y releasing a considerable quantity of the fluid from the cylinder E in advance of the now relatively fast travelling ram 5. As before explained this is accomplished by opening the surge valve. It will be obvious, however, that any sudden opening of 'the surge valve would subject the whole system to considerable shock which is detrimental and, therefore, undesirable. It is an object of my present invention to provide means for assuring a gradual opening of the surge valve. I accomplish this by use of mechanism which I will now proceed to describe.

In order to thus control the operation of the surge valve 4I provide a surge valve operation control unit K, and I prefer to mount this unit die rectly in the surge tank so as to avoid the necessity of pipingA connections between the unit and the surge tank.

The control unit K comprises a casing 35 having a pressure chamber 36 communicating through a valve controlled passage 37 including a seat 38 with a chamber 39 which communicates directly with lthe fluid within the surge tanlr G. r The unit may, of course, be mounted outside the tanir andindirectly connected therewith by a pipe connectn ed with the chamber 39 if desired.

The casing 35 is provided at its upper end with a threaded bore to receive a vented valve guide.

cap l0 which serves as a guide for the check valve di which cooperates with the seat 38 and which is biased to closed position, in the present instance by gravity. The casing is also provided with a lower bore ft2 closed by a screw cap i3 and providing a pressure chamber which is separated from the chamber 39 by a wall Alt. Ihe wall le is equipped with a guide d to slidably and snugly receive the plunger #i5 which projects upwardly through the guide i5 into close provimity with the valve 1li and is provided at le and serving to hold the plunger' against the'screw cap e3 and with its upper end just out vci contact with the valve al. The control unitcliarnber is in conm stant communicationy with the pressure chamber 3i oi the surge valve casing .through a pipe d3, and through a pipe 49 inlet and ,outlet ports of the reversible pump H. rl'his same port of the pump is connected by a pipe line 50 with the push-back cylinders as illustrated in Figure 2 of the drawings. The other pump port 51 is connected by a` pipe line 52 with the main cylinder E, a branch 53 of this pipe being connected to communicate, through a duct provided in the screw cap d3, with the pressure chamber provided by the lower bore d2 so that pressure within the pipe line 52, 53 will act against the plunger d6, e7.

The control mechanism generally designated I and disclosed in detail in Patent 1,711,378 hereinbeiore referred to is designed to cause the platen to operate through a complete working stroke and retractive stroke cycle. The control lever of `this mechanism, generally designated 5d, when depressed, sets into motion the mechanism for causing the reversible pump to operate in a direction for forcing the platen, which has previously travelled into engagement with the work by action o gravity, to actively press the workpositioned thereunder. As will beevident after perusal of the patent just abovereferred to, the pressure built up during this opera ive? function of the its lower end with a y head e7, the latter being engaged by a spring in- :terposed between it and the wall with one of the combinedy platen will automatically act to effect a reversal of the pump cylinders F into control for retracting or elevating the platen. The pressure pipe line for bringing about communication of this built-up pressure from the main cylinder to pump is generally inand thereby bring the push-back sol dicated at 55 and the trip devices disclosed in detail in the patent referred to and which serve to readjust the pump to throw it into neutral when the platen -has reached a suitable retracted position are generally indicated at 56. Through this mechanism described as stated inU. S. Letters Patent No. 1,711,378 of April 30, 1929, the platen is caused to act upon the work and then automatically return to its elevated position whereupon the pump is adjusted to an inactive condition.

In operation, the platen descends by gravity until it cornes in contact with the work,the oil from the surge tank passing through the surge valve to lill the evacuated space above the main ram 5 in the cylinder E as previously described. As soon as the platen comes in contact with the work, the check valve closes. Pressure will now build up in the system, iiowing through the pipe line 52 into cylinder E. This pressure will act through the branch `line 53 to actuate the plunger i 46, li7 and 'force open the check valve 4l, allowing the pump to take its suction freely through pipe line i9 and chambers 36 and 39 from the surge 'tank G. When the press platen movement is will build up and act, through the chamber 36 and U pipe line d8, to iorce downwardly the plunger 29 to unseat the surge valve. ln .this manner the surge valve is opened gradually, after pressure in the main cylinder E has been suitably reduced, and thus the system is relieved of the shock-and other parts relieved of the strain which'would be occasioned by suddenly 'orcing open the surge valve while pressure within the main cylinder E was at its maximum :just after completion oi the pressing function. This mechanism also maires it possible to employ a surge valve of maximum diameter so as to provide for the ireest possible communication between the main cylinder E and the surge tanlr G.

After pressure within the cylinder E is thus suitably reduced, the push-back rams 7, heretofore resisted by the great pressure within the main Ill@ mit

. ist

cylinder E,are acted upon by pump pressure built up in the pipe line'50 to return the platen to its elevated position.

Although the invention has been shown by way' of illustration as being embodied in a circuit ln'- cluding a press having separate main and auxiliary rams, it will be understood that the invention also may be used in connection with presses having a single double acting ram, one face oi which acts to advance the ram and the lower face its `second conduit "communicating between the I claim:

1. In apparatus of the character described wherein is provided a platen, a main cylinder and main ram for moving the platen in one direction, an auxiliary cylinder and auxiliary ram for moving the platen in the opposite direction, a surge tank, a surge valve to open communication at times between the surge tank and the main cylinder, means including a hydraulic pressure circuit and a pump operable to exertI fluid pressure against the main cylinder ram to project the platen and reversible to exert fluid pressureagainst the auxiliary cylinder ram to retract the platen, and means active upon each reversal of the pump from the platen projecting to the platen retracting condition for rst bringing about a reduction of pressure in the main cylinder and thereafter positively opening' the surge valve, said last named means including a surge valve operation control unit comprising a casing having a pressure chamber in communication with the pressure circuit and being adapted to communicate through a by-pass with the surge tank, a check valve in said by-pass and being biased to closed position, a pressure responsive check valve opening plunger mounted for movements in said chamber, said check valve opening plunger being active upon subjection to high pressure for unseating and holding unseated the check valve, a spring engaging said plunger and urging the latter to inactive position, and a pressure duct for subjecting the check valve opening plunger to the pressure within the main cylinder.v

2. In apparatus of the character described wherein is provided a platen,y a main cylinder and main ram for moving the platen in one direction, an auxiliary cylinder and auxiliary ram for moving the platen in the opposite direction, a surge tank, a surge valve to open communication at times between the surge tank and the main cylinder, means to apply pressure to the rams to eiect movement thereof including two fluid conduit lines alternately active to supply and withdraw fluid respectively from the main and auxiliary cylinder, pressure responsive surge valve opening means, a surge valve control unithaving a pressure chamber,- a, second chamber in constant communicationwith the surge tank, a conduit 'communicating between the pressure chamber and the 'auxiliary cylinder conduit, a

pressure chamber and the pressure responsive opening means, a check valve in the control unit -controlling communication between the pressure and -secondjchambers thereof and being biased to closed position, and means biased to .inactive position and being responsive to pressure in the main cylinder for being moved to active position to unseat said check valve during high pressure conditions in the main cylinder.

3. In apparatus of the character described wherein is provided a platen, a mainl cylinder and main ram for moving the platen in one direction, an auxiliary cylinder and auxiliary ram for moving the platen in the opposite direction, a surge tank, a surge valve to open communication at times between the surge tank and the main cylinder, means to apply pressure to the rams to` effect movement thereof including two iluid conduit lines alternately active to supply and withdrawl iluid respectively from the main and auxiliary cylinder, pressure responsive surge valve opening means, a surge valve control unit having a pressure chamber, a second chamber in constant communication with the surge tank, a

conduit communicating between the pressure chamber and the auxiliary cylinder conduitpa seond conduit communicatingbetween the pressure chamber and the pressure responsive opening means, a gravity seated check valve in the control unit controlling communication between the pressure and second chambers thereof, said unit also having a plunger chamber, a plunger projecting into the plunger chamber and adapted when active to engage said check valve for opening the latter, means for biasing said plunger to inactive position, and a branch conduit cornmunicating with the plunger chamber and with the main cylinder to subject the plunger to fluid pressure in said main cylinder.

4. In apparatus of the character described wherein is provided a platen, a main cylinder and main ram for moving the platen in one direction, an auxiliary cylinder and auxiliary ram for moving the platen in the opposite direction, a surge tank, a surge valve to open communication at times between the surge tank and the main cylinder, means to applypressure to the rams to eiect movement thereof including two iluid conduit lines al.ernately active to supply and withdraw iluid respectively from the main and auxiliary cylinder, pressure responsive surge valve opening means, a surge valve control unit having a pressure chamber, a second chamber in constant communication with the surge tank, a conduit communicating between the pressure chamber and the auxiliary cylinder conduit, a second conduit communicating between the pressure chamber and the 'pressure responsive .opening means, a check valve in the control unit controlling communication between the pressure and second chambers ihereof and being biased to closed position f means active in response,v to pressure in the main cylinder to hold the check valve unseatedduring high pressure conditions in the main cylinder, and a biasing spring for urging said means to inactive position to permit said check valve to seat upon relief of said highpressure condiion and enable pressure in the pressure chamber to build up and bring about actuation of the surge valve opening means. 5. Inanappara'tus of the character described wherein is provided a platen, a main cylinder and main ram for moving the platen in one direction, an auxiliary cylinder and auxiliary ram for moving the platen in the opposite direction, a surge tank, a surge valve to open communication at times between the surge tank and the main cylinder, means including a hydraulic pressure circuit and a pump operable to exert uid pressure against the main cylinder ram to project the platen and to exert fluid pressure against the auxiliary cylinder ram to retract the platen, and means active at the end of a stroke under main ram drive' for rst bringing about a reduction of pressure in the main cylinder to permit openingv of said surge valve, said last named means including a casing having a pressure chamber in communication with said auxiliary cylinder and being adapted to communicate with said surge tank, a check valve for controlling communication between said chamber and surge tank and' being biased to closed position, means defining a vseparate pressure chamber, means providing communication between said second pressure chamber and said main cylinder, a bore in a Wall `of said second chamber, and a plunger extending through and tting snugly in said bore for sliding movements and being adapted to respond to pressure in said main cylinder for being moved to active position to open said check valve and beingbiased to inactive position.

6. In a hydraulic press circuit, the combination yof a presshavingmain and ram-returning cylinders and cooperating ram means; a pump; a pipe line affording communication between said pump and said main cylindera pipe line affording communication between said pump and said ramreturning cylinder; means for reversing the iiow of fluid in said pipe lines; a surge tank; a surge Valve interposed between said tank and said main cylinder and biased to closed position; means deiining a pressure chamber; a pressure responsive plunger'therein adapted to open said surge said device`in one direction only for normally holding said device in inactive position; and a branch pipe interposed between said main cylinder and said second pressure chamber.

WALTER ERNST. 

